A known seat adjustment apparatus for adjusting a position of a seat cushion in an up-and-down direction (a vertical direction) is disclosed in JP2109194Y, which will be hereinafter referred to as Reference 1. As illustrated in FIG. 17, the seat adjustment apparatus disclosed in Reference 1 includes a ratchet 201 and a pawl 206 each of which is rotatably connected to a bracket holding the seat cushion. The ratchet 201 and the pawl 206 engage with each other at a position away from respective rotational axes of the ratchet 201 and the pawl 206. The pawl 206 is normally biased by a turnover spring 209 in a direction to engage with the ratchet 201, i.e., in an engagement direction.
Accordingly, the ratchet 201 is allowed to rotate in a counterclockwise direction in FIG. 17 where an engagement position between the ratchet 201 and the pawl 206 is separated from the rotational axes thereof. In addition, the rotation of the ratchet 201 in a reverse direction, i.e., a clockwise direction in FIG. 17, is restricted. The engagement position between the ratchet 201 and the pawl 206 moves to thereby adjust and maintain the position of a front portion of the seat cushion in the up-and-down direction.
In a case where the rotation of the ratchet 201 in the counterclockwise direction in FIG. 17 is proceeded and thus a first protruding portion 202 of the ratchet 201 engages with a projection 207 of the pawl 206, the turnover spring 209 is turned over in association with the rotation of the pawl 206. As a result, the ratchet 201 and the pawl 206 are inhibited from engaging with each other. On the other hand, in a case where a second protruding portion 203 presses an engagement surface 208 of the pawl 206 in association with the rotation of the ratchet 201 in the clockwise direction in FIG. 17 from the aforementioned state where the ratchet 201 and the pawl 206 are inhibited from engaging with each other, the turnover spring 209 is turned over in association with the rotation of the pawl 206 so that the pawl 206 returns to an initial position or an initial state. Accordingly, the position of the front portion of the seat cushion may be again adjusted and held.
In addition, JP2010-35862A, which will be hereinafter referred to as Reference 2 discloses an armrest apparatus serving as the seat adjustment apparatus. As illustrated in FIG. 18, the armrest apparatus disclosed in Reference 2 adjusts and holds an angle of an armrest body relative to a seat frame by means of operations of a cam member 211 fixed to a shaft and a release block 216, and a contraction of a lock spring 219 wound on the shaft. In a case where the armrest body is rotated in a retracting direction from a usage state, the lock spring 219 is enlarged so that the armrest body is rotatable. In a retracted state of the armrest body, the enlarged state of the lock spring 219 is maintained. On the other hand, in a case where the armrest body is rotated in a deploying direction from the retracted state, the lock spring 219 is compressed so as to inhibit the armrest body from rotating. Accordingly, the angle of the armrest body relative to the seat frame may be adjusted and held in a non-step manner.
Further, WO2008/004696A1, which will be hereinafter referred to as Reference 3, discloses an ottoman device serving as the seat adjustment apparatus. The ottoman device disclosed in Reference 3 adjusts and holds or maintains the position of an ottoman in the up-and-down direction.
According to Reference 1, an axial misalignment of the ratchet 201 and the pawl 206, each formed by a plate member, at the engagement position may not be restricted and therefore the seat may not be stably held. At this time, it may be restricted to provide an appropriate member, for example, a stopper for a restriction of the axial misalignment of the ratchet 201 and the pawl 206 because of the arrangement of the turnover spring 209 adjacent to the pawl 206 in the axial direction.
In addition, according to Reference 2, a structure for the contraction of the lock spring 219, i.e., the cam member 211 and the release block 216, is necessary so as to adjust and maintain the angle of the armrest body relative to the seat frame, which may lead to an increase of components and a complex configuration. According to Reference 3, the same issue as Reference 2 may be raised.
A need thus exists for a seat adjustment apparatus for a vehicle which is not susceptible to the drawback mentioned above.